1. Field of the Invention
The present invention relates to a method of and an apparatus for controlling a motor-driven let-off motion for use in a loom.
2. Description of the Prior Art
Control systems for controlling motor-driven let-off motions for looms have a tension compensator for detecting any variation in the tension of warp yarns during weaving to compensate for deviations or errors in the control system.
The tension of warp yarns is subjected to ripples due to major motions of the loom while the main shaft of a loom makes one revolution. Such tension ripples during one revolution of the main shaft are not usually placed under control. The tension compensator includes an integrating circuit having a large time constant to provide an integrating capability for taking up the tension ripples while the main shaft makes one revolution. The integrating capability however makes the conventional control system slow in detecting warp tension. As the diameter of warp coils on beams is reduced as the weaving progresses while the loom is in operation, a tension compensation gain is relatively changed so that optimum control cannot be achieved. Since an integrating capacitor is discharged when the weaving is interrupted, the operating condition prior to the interruption of the weaving cannot be reached when the loom is restarted, resulting in poor restarting characteristics.